Method for improving wet crease recovery



United States Patent 3,505,002 METHOD FOR IMPROVING WET CREASE RECOVERY Everett H. Hinton, Jr., Vernon C. Smith, and Robert L.

Jones, Greensboro, N.C., assignors to Burlington Industries, Inc., Greensboro, N.C., a corporation of Delaware No Drawing. Filed Dec. 21, 1965, Ser. No. 515,480 Int. Cl. D06m 13/14, 13/34 US. Cl. 8"116.3 1 Claim ABSTRACT OF THE DISCLOSURE A process for increasing the wet crease recovery of a cellulosic textile which comprises treating the same with a nitrogenous product which has a reactive nitrogen and film-forming properties, thereafter wetting and swelling the textile, and then' treating the wet, swollen textile in an acidified dehydrating formaldehyde solution.

The present invention relates to a method for improving the wet crease recovery of cellulose textiles. More particularly, the invention is concerned with a novel treatment of cellulose textiles involving the sequential application of one or more nitrogenous compounds as defined erein and formaldehyde whereby wet crease recovery and other properties are advantageously improved.

It is well known that certain types of nitrogen-containing compounds, such as ureas, melamines, carbamates and the like can be reacted with formaldehyde under alkaline conditions to produce methylolated products which may be used to stabilize cellulosics and impart crease recovery -primarily dry crease recovery. While the methylolated products may be formed in situ on the textile, they are generally prepared beforehand and applied by conventional padding, drying and curing in the presence of an acid-type catalyst. This practice suffers from several disadvantages. For one thing, premethylolation using alkaline conditions requires a substantial period of time. Acid conditions have been tried for the methylolation reaction but this usually results in premature polymerization, gellation or cross-linking and is undesirable and unworkable if done before application to the textiles. Then, too, premethylolation products have a very strong odor which is objectionable. Stability and bath life in the presence of an acid catalyst is limited and steps must be taken to protect the methylolation products from heat. Other problems are inherent when in situ methylolation is employed. In either case, the treatment usually results only in an increase in dry crease recovery or a preference therefor over wet crease recovery.

It is also well known that cellulosic textiles can be reacted with acid catalyzed formaldehyde to impart or improve crease recovery. The known procedures may be designed to either preferentially improve dry or wet crease recovery or provide a compromise combination of dry and wet crease recovery. These procedures may be of the batch type wherein the fabric is padded with formaldehyde followed by long wet reaction times or they may involve pad-dry-cure techniques. In either case, however, there are limitations on the amount of crease recovery.

In view of the above, the principal object of the present invention is to provide a process for treating a cellulosic fabric which obviates prior art problems and gives unexpectedly high wet crease recovery in conjunction with other desirable properties. Other advantages will also be hereinafter apparent from the following detailed description of the invention.

Broadly stated, the present process involves 1) pretreating the cellulosic textile, preferably in fabric form, with a nitrogen-containing product as hereinafter defined;

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(2) optionally drying; (3) then Wetting and swelling the cellulosic in water; and (4) reacting the cellulosic in the wet, swollen condition in a dehydrating, acid catalyzed formaldehyde medium, followed by (5). drying and, when and if desired, (6) curing.

This combined application of nitrogenous compound and formaldehyde in the sequence indicated has been found to give a remarkably and unexpectedly high wet crease recovery. This is very surprising because the nitrogenous product by itself imparts very little wet crease recovery to the textile while the sequential application of this product and formaldehyde as described gives a wet crease recovery greatly in excess of that obtainable using the formaldehyde treatment alone. It is not clear what reaction, if any, takes place between the nitrogenous compound and the formaldehyde but Whatever the reaction or phenomenon may be, it is apparent that it occurs rapidly and makes possible a continuous operation. Additionally, the process effectively eliminates the need for any premethylolation and prior odor and bath stability problems are effectively avoided.

Without being limited to any particular theory of operation, one possible explanation for the unexpected increase in wet crease recovery obtained herein is that rapid partial methylolation of the nitrogenous compound occurs under the prevailing acid conditions. If this reaction occurs, it must do so in an extremely rapid fashion since the treatment with formaldehyde herein may be effectively conducted in thirty seconds or less. This is a much shorter time than conventional type methylolation reactions. As a possible alternative to methylolation, or in addition thereto, the reaction of formaldehyde with the nitrogenous product may link the resulting product with the cellulose. A third possible explanation is that crosslinking of the cellulose is enhanced by the presence of the selected nitrogen-containing product. For example, the presence of the nitrogenous product may act to concentrate the formaldehyde reactant and catalyst in the proper position in the cellulose to cause the surprising result observed herein. This effect may be due to optimum control of the water content of the cellulose, which is of primary importance in the preferred crosslinking process, by the formation of a film by the nitrogenous product on the cellulose, the film acting as a permeable membrane which allows the water and other reactants necessary for reaction to be retained in the optimum amount. In this connection, it is noted that the preferred nitrogenous products used herein are excellent film formers.

As another possible explanation, it may be that the formaldehyde process causes reaction of the nitrogenous product with itself to form a homopolymer, .which is linear or crosslinked in a three-dimensional network. This effect could be concurrent with crosslinking of the cellulose.

The nitrogenous products used herein are distinguished from the ureas, melamines, triazines, triazones, and the like conventionally employed with formaldehyde in the form of methylolation products. More particularly, the nitrogenous products employed in the present case are characterized by the fact that they contain at least one reactive nitrogen atom. In addition, these products should be good film-formers as noted earlier. The preferred products are polymeric amines or amides. Examples of the most effective nitrogenous products are polyacrylamide (e.g. Cyanamer P250, a polyacrylamide having a molecular weight of approximately 5 million to 6 mil lion) and the partially deacetylated polymer of N-acetyl- N-glucosamine (Kylan LV). Other nitrogencontaining products of varying film-forming nature which may be used herein include polyvinyl pyrrolidone, aminized soy bean oil, aminized amylose (approximately 1 nitrogen atom per 5 glucose units) and the polyamide of an ethylene diamine derivative and a 36 carbon dibasic acid. Amines such as glucosamine and triethylene tetramine of lower film-forming ability may also be used.

The amount of the nitrogenous product used herein can be varied within wide limits. In general, the upper limit is established by the hand of the treated fabric and economic considerations while the lower limit is dependent upon the amount of wet wrinkle recovery desired in the final product. However, as an example, it may be noted that as low as 0.1% of the nitrogenous compound, based on the weight of the untreated fabric, produces a significant increase in the wet wrinkle recovery of the fabric. The preferred amount of the nitrogenous product usually falls in the range of about 0.35% to about 1.0% by weight of the untreated fabric. This amount may vary according to the crease recovery desired, tactile hand of the fabric desired, and other properties.

The fabric to be treated in accordance with the process of the invention may be pretreated, e.g. bleached and mercerized. Care, however, should be taken to completely wash off caustic alkali along with other residual or excess chemical agents before subjecting the fabric to the process of the invention. Excess chemical agents, such as free alkali, if left on the fabric, reduce or prevent the full attainment of the advantages of the process herein.

The nitrogenous product is advantageously applied by padding from aqueous solution or dispersion containing the product. The concentration of such composition should be adequate to conveniently give the desired solids pickup. Thereafter, the fabric is preferably, but not necessarily, dried. Drying conditions will vary widely depending on other factors, but typical temperatures are 225- 300 F. for 1 to 3 minutes. 'It may then be advantageous to give the fabric a further heat treatment, at, for example, 325-375 F. for /22 minutes to insure best results.

After treatment with the nitrogenous product as described, the textile is wet and swelled with water and then treated as described above with formaldehyde. Advantageously, the wetting and swelling and formaldehyde treatment are carried out using the process described in copending application Ser. No. 156,859, filed Dec. 4, 1961, now U.S. Patent No. 3,371,983, issued Mar. 5, 1968, the subject matter of which is incorporated herein by reference. More particularly, the textile is padded with an aqueous bath which may be substantially pure water or it may contain a small amount, preferably 0.11%, of a wetting agent. If the textile is of the type which wets out, the wetting agent may be omitted and plain water can be employed. While anionic and cationic wetting agents may be used, the preferred .wetting agents are nonionic in character.

In the aqueous bath, the cellulosic textile is padded to pick up about 10100%, preferably 60-70%, of water, based on the weight of the textile.

Substantially immediately after the textile has been padded with water, with or without the wetting agent, the wet and swollen textile is impregnated with a dehydrating solution containing formaldehyde. The formaldehyde content of the solution is usually 5-15 but can be lower, e.g., 3%, or higher, e.g., This formaldehyde solution also contains a dehydrating agent and a strong acid. As the dehydrating agent there can be employed glacial acetic acid or calcium chloride. The amount of the dehydrating agent which may be used can be varied within a wide range. Generally, however, between about to 70% of the the dehydrating agent based on the weight of the formaldehyde solution is preferred and between to 60% is particularly preferred.

As the strong acid, there can be employed phosphoric acid, hydrochloric acid, hydrobromic acid, sulfuric acid, trichloroacetic acid, formic acid and toluene sulfonic acid. The acid strength in the formaldehyde solution can vary from moderate concentrations, e.g., 20% to as low as 0.1%, but preferably is between 0.3 and 6%. The preferred acid is hydrochloric acid. Instead of having the acid in the dehydrating solution, the acid may be employed in the aqueous bath immediately preceding the dehydrating treatment step. Acid and formaldehyde may also be added to the aqueous bath prior to the dehydrating step, for the purpose of maintaining acid and formaldehyde concentrations better in the dehydrating bath over long running periods. In any event, to formaldehyde reaction is carried out under strongly acid conditions, i.e., pH of about 1 or even lower.

All of the chemical compounds used in the formaldehyde solution, i.e., the formaldehyde, the strong acid and dehydrating agent, are employed in the commercial forms but are stated in anhydrous percentages in the examples.

The invention is further illustrated but not limited, by the following specific examples. Unless otherwise indicated, all percentages herein are by weight.

EXAMPLE 1 Bleached and mercerized cotton broadcloth containing approximately 144 warp threads and 62 filling threads was thoroughly washed to completely remove any alkali or other residual unreacted chemical agents, and then dried. Four samples of this fabric were then processed as follows:

Samples 1 No treatment. 2 Treated with formaldehyde bath only. 3 Treated with nitrogenous product only. 4 Treated with both the nitrogenous product and formaldehyde bath.

Only the procedure for treating Sample 4 is given below since the formaldehyde bath and the solution containing the nitrogenous product used for Samples 2 and 3, respectively, were the same as those employed for Sample 4.

Sample 4 was first padded with a 1% by weight solution of Cyanamer P-250 to obtain a 70% pick-up of the solution. The wet fabric was then dried at 250 F. and heated for 1.5 minutes at 350 F.

The dried fabric was then padded with water to obtain a 70% wet pick-up and substantially immediately thereafter passed into a formaldehyde reaction bath containing the following ingredients:

Percent Formaldehyde (anhydrous) 16.2 Hydrochloric acid (anhydrous) 0.5 Calcium chloride (anhydrous) 36.5 Water 46.8

TABLE I Tensile Angle Warp-l-Filling Percent Strength Wash Bound Warp] Dry Wet Wear Formal- Sample Filllng Crease Crease Rating dehyde 1 (Control)-.. /60 134 142 2. 3 2 (F) 47/28 181 259 3. 7 3 N 89/65 144 193 4 (N+F). 51/20 197 308 3. 5

From the above table it can be seen that Sample 4, which was treated with polyacrylamide before the formaldehyde treatment, produced much higher wet crease recovery than Sample 2, which was only treated with the formaldehyde bath, even though both samples contained about the same amount of bound formaldehyde. Furthermore, Sample 4 showed less overall tensile strength loss than Sample 2. When the strength losses for the two samples are converted to loss per unit of wet crease recovery obtained, the strength loss for Sample 4 is even less than indicated in Table I. The wash-wear ratings of the two samples are about the same.

A small wet crease recovery is noted for Sample 3, which was treated only with polyacrylamide, as compared to the control, Sample 1.

EXAMPLE 2 Example 1 was repeated except that the treatment with the nitrogenous product was carried out by padding the fabric with a solution containing 0.5% of Kylan LV-100 and 0.5 acetic acid to obtain a 70% wet pick-up. The results of this example are summarized in Table II below wherein Samples 5-8 were given the same formaldehyde processing as Samples l4, respectively, of Example 1. Samples 9 and 10 correspond to Samples 6 and 8, respectively, except that Samples 9 and 10 were additionally treated after the formaldehyde treatment by padding with a 0.6% solution of anhydrous magnesium chloride, dried at 250 F. and heated for 1.5 minutes at 350 F.

TABLE II Tensile Angle Warp +Fi1ling Strength, M Wash-Wear Sample Warp/Filling Dry Crease Wet Crease Rating 5 (Control). 90/60 134 142 2. 3 6 F 47/28 181 259 3. 7 86/62 143 176 9 (F /20 233 245 3. 10 (N+F) /21 239 264 EXAMPLE 3 A sample of fabric similar to that used in Example 1 was treated with a 1.0% by weight solution of deacetylated N-acetyl glucosamine and 1% acetic acid following the application, drying and heating before formaldehyde reaction as in Example 2. Reaction conditions were the same as in Example 1 for both the treated and untreated control fabrics. The results for the fabric treated according to the invention were as follows:

TABLE III Sample 11:

Tensile strength warp/ filling 47/33 Dry crease angle warp+filling 178 Wet crease angle warp+filling 310 Wash/wear rating 3.0 Percent bound HCHO 0.96

It will be noted that the wet crease angle for Sample 11 is 310. This is substantially and unexpectedly higher than the values obtained using formaldehyde alone (Samples 2 and 6).

EXAMPLE 4 A sample of fabric similar to that used in Example 1 was divided into four portions and identified as Samples 12-15, inclusive. A 0.5% deacetylated N-acetyl glucosamine solution (containing 0.5 acetic acid) was applied to those four samples using the procedure of the preceding examples except that, in the case of Samples 14 and 15,

the heat treatment at 350 F for 1 /2 minutes was omitted. The results are summarized below:

TABLE IV Tensile Angle Warp +Flling Strength, Wash-Wear Sample Warp/Filling Dry Crease Wet Crease Rating 12 (N) 86/62 161 164 13 (N-l-F) 48/25 203 304 3. 5 14 N 88/56 149 179 15 (N-l-F)*.. 50/23 203 306 4. 0

Drying only, no subsequent heat treatment.

From the Table IV results, it will be noted that the heat treatment does not significantly change the wet or dry crease angle although it does appear to improve the durability of the fabric (for example, to laundering, etc.).

EXAMPLE 5 Percent Formaldehyde (anhydrous) 8.0 HCl (anhydrous) 0.5 Calcium chloride (anhydrous) 35.0 Water 56.5

The temperature of the bath was kept at 65 C. and the samples were immersed in the bath for 35 seconds. The results obtained are as follows:

TABLE V Tensile Angle Warp-l-Filling Percent Strength, Bound Form- Sample Warp/Filling Dry Crease Wet Crease aldehyde 16 (N+F) 68/42 158 273 0. 35 17 (F) 67/43 168 225 0. 35

The data in Table V indicates that a desired level of wet crease recovery can be obtained by varying other reaction conditions, the unexpected dilference in wet crease angles between fabric. processed according to the invention (Sample 16) and fabric treated with formaldehyde only (Sample 17), being maintained for the same bound formaldehyde content.

EXAMPLE 6 Cotton army twill was divided into three samples (Samples 18-20, inclusive). Of these samples, Sample 18 was treated at 7679 C. for 30 seconds in a formaldehyde bath similar to that of Example 1. Sample 19 was padded with an aqueous solution containing 0.5% deacetylated N-acetyl glucosamine and 0.5% acetic acid, dried at 250 F. and heated at 350 F. for 1.5 minutes. Sample 20 was given both treatments, i.e., it was padded with the solution of deacetylated N-acetyl glucosamine and acetic acid, dried at 250 F., heated at 350 F., for 1.5 minutes and then given the formaldehyde treatment. Samples 18 and 20 were padded with water before entering the formaldehyde reaction just as in Example 1. The results for each sample are listed below:

aqueous solution containing 0.65% deacetylated N-acetyl glucosamine and 0.65% acetic acid, dried at 250 F., and heated at 350 F., for 1.5 minutes. Samples 21 and 22 were then passed through the aqueous pretreating step and then into the formaldehyde bath of Example 1 using the conditions disclosed therein. The results obtained for these samples were:

TABLE VII Tensile Angle Warp +Filling Strength, Wash/Wear Sample Warp/ illing Dry Crease Wet Crease Rating 21 (F) 48/34 212 210 3. 22 (N+F) 45/40 180 240 3. 0

This example illustrates the fact that the present process is useful in the treatment of rayon to effect an important increase in wet crease recovery.

EXAMPLE 8 Example 3 was repeated except that the 1% aqueous solution of the deacetylated polymer of N-acetyl glucosamine was replaced with a 1% aqueous solution of glucosamine itself (as distinguished from the polymer). The results so obtained are summarized in Table VIII below.

Example 1 was repeated except that the 1% solution of polyacrylamide was replaced by a 1% solution of a polyamide made from an ethylene diamine derivative and dibasic acid containing 36 carbon atoms. The results obtained with the cotton broadcloth fabrics so treated are given in Table IX wherein Samples 27 to 30 correspond to Samples 1 to 4, respectively, of Example 1 with respect to the treatment received by the samples.

TABLE IX Tensile Angle Warp+Filling Percent Strength, Bound Sample Warp/Filling Dry Crease Wet Crease Formaldehyde 27 (Control). 93/57 138 134 28 (F) 51/30 155 252 0. Q2 20 (N) 88/51 159 30 (N+F) 49/26 176 278 0. 89

As will be noted, Sample 30 showed a much higher wet crease angle than the other samples, including the formaldehyde treated sample (Sample 28) where bound formaldehyde was at the same level.

It will be appreciated that various modifications may be made in the invention described herein. Because of the extremely short period of time involved for the formaldehyde treatment, the process can be made continuous by using a series of appropriate pads followed by drying and curing as needed and as shown above.

The scope of the invention is defined in the following claim wherein:

We claim:

1. In a process for treating a cellulosic textile by wetting and swelling the textile with water and then immersing the wet, swollen textile in an acidified dehydrating formaldehyde solution, drying and curing, the improvement for increasing the wet crease recovery of said textile, said improvement comprising impregnating the textile with an aqueous solution of a water-soluble film-forming polyacrylamide of molecular weight approximately 5-6 million and drying the thus impregnated textile prior to wetting and swelling with water.

- References Cited UNITED STATES PATENTS 2,200,944 5/1940 Wood 81l6.3 2,272,489 2/ 1942 Ulrich 2528.8 2,361,270 10/1944 Collins et al 8116.2 X 2,901,813 9/1959 Schappel 8116.2 X 3,046,079 7/1962 Reeves et al 8-1163 X 3,094,371 6/1963 Vanloo et al 8-1l6.2 3,102,773 9/1963 Needleman 8116.3 3,371,983 3/1968 Barber et al 8116.3 X

HERBERT B. GUYNN, Primary Examiner US. Cl. X.R. 

